Electrosurgical devices configured for use with a dry tip use electrical energy, most commonly radio frequency (RF) energy, to cut tissue or to cauterize blood vessels. During use, a voltage gradient is created at the tip of the device, thereby inducing current flow and related heat generation in the tissue. With sufficiently high levels of electrical energy, the heat generated is sufficient to cut the tissue and, advantageously, to stop the bleeding from severed blood vessels.
Current dry tip electrosurgical devices can cause the temperature of tissue being treated to rise significantly higher than 100° C., resulting in tissue desiccation, tissue sticking to the electrodes, tissue perforation, char formation and smoke generation. Peak tissue temperatures as a result of RF treatment of target tissue can be as high as 320° C., and such high temperatures can be transmitted to adjacent tissue via thermal diffusion. Undesirable results of such transmission to adjacent tissue include unintended thermal damage to the tissue.
Using saline to couple RF electrical energy to tissue inhibits such undesirable effects as sticking, desiccation, smoke production and char formation. One key factor is inhibiting tissue desiccation, which occurs if tissue temperature exceeds 100° C. and all of the intracellular water boils away, leaving the tissue extremely dry and much less electrically conductive. However, an uncontrolled or abundant flow rate of saline can provide too much cooling at the electrode/tissue interface. This cooling reduces the temperature of the target tissue being treated, and the rate at which tissue thermal coagulation occurs is determined by tissue temperature. This, in turn, can result in longer treatment time to achieve the desired tissue temperature for treatment of the tissue. Long treatment times are undesirable for surgeons since it is in the best interest of the patient, physician and hospital to perform surgical procedures as quickly as possible.
RF energy delivered to tissue can be unpredictable and often not optimal when using general-purpose generators. Most general-purpose RF generators have modes for different waveforms (e.g. cut, coagulation, or a blend of these two) and device types (e.g. monopolar, bipolar), as well as power levels that can be set in watts. However, once these settings are chosen, the actual power delivered to tissue and associated heat generated can vary dramatically over time as tissue impedance changes over the course of RF treatment. This is because the power delivered by most generators is a function of tissue impedance, with the power ramping down as impedance either decreases toward zero or increases significantly to several thousand ohms. Current dry tip electrosurgical devices are not configured to address a change in power provided by the generator as tissue impedance changes or the associated effect on tissue and rely on the surgeon's expertise to overcome this limitation.
One medical condition which employs RF energy in treatment is gastrointestinal (GI) bleeding, with such treatment typically administered via gastrointestinal endoscopy. Bleeding in the upper gastrointestinal tract may result from, for example, peptic ulcers, gastritis, gastric cancer, vascular malformations such as varices (e.g. esophageal) and other lesions. Bleeding in the lower gastrointestinal tract may result from, for example, vascular malformations such as hemorroidal varices.
Peptic ulcer bleeding is one of the most common types of non-variceal upper gastrointestinal bleeding. Peptic ulcer bleeding results from the combined action of pepsin and hydrochloric acid in the gastric or digestive juices of the stomach. Peptic ulcers further include, for example, gastric ulcers, an eroded area in the lining (gastric mucosa) of the stomach, and duodenal ulcers, an eroded area in the lining (duodenal mucosa) of the duodenum. Peptic ulcers may also be found in Meckel's diverticulum.
Endoscopic modalities for the treatment of upper gastrointestinal bleeding include injection therapy (e.g. diluted epinephrine, sclerosants, thrombogenic substances, fibrin sealant), mechanical clips and so called thermal (heating) methods. Thermal methods are often divided into so called non-contact thermal methods and contact thermal methods. Non-contact thermal methods include laser treatment and, more recently, argon plasma coagulation (APC). Thermal contact methods include multipolar electrocoagulation and thermal coagulation probes.
Non-contact thermal probe methods depend on the heating of tissue protein, contraction of the arterial wall and vessel shrinkage. One drawback of non-contact thermal methods is the “heat sink effect” where flowing arterial blood leads to dissipation of the thermal energy. Because of the greater tissue penetration, the neodymium: yttrium aluminum garnet (Nd:YAG) laser is generally superior to the argon laser for ulcer hemostasis. In any event, laser units are expensive, bulky and generally not portable. They are also difficult to use as an en face view of the bleeding ulcer is often required. For these reasons, laser photocoagulation has generally fallen out of favor for the treatment of ulcer bleeding. The argon plasma coagulator uses a flowing stream of argon gas as the conductor for electrocoagulation. This method is generally effective for mucosal bleeding but may not be effective in coagulating an eroded artery in a bleeding ulcer. Also, as flowing gas is required, care must be taken to avoid overdistention of the stomach during treatment.
Contact thermal probes utilize the principle of “coaptive coagulation”. First, mechanical pressure is applied to the bleeding vessel to compress the vessel before heat or electrical energy is applied to seal the bleeding vessel. Compression of the blood vessel also reduces the blood flow and reduces the heat sink effect. Multiple pulses of energy are given to coagulate the bleeding vessel to achieve hemostasis. These methods are effective in hemostasis but carry a potential risk of inducing bleeding when an adherent probe is pulled off a bleeding vessel. Furthermore, contact devices require accurate targeting of the bleeding vessel for successful ulcer hemostasis.
Multipolar electrocoagulation devices include the BICAP® Hemostasis Probe from ACMI Circon (300 Stillwater Avenue, Stamford, Conn. 06902) and the Gold Probe™ from Microvasive (480 Pleasant Street, Watertown, Mass. 02172). A third multipolar electrocoagulation device is the Injector-Gold Probe™, also from Microvasive, which incorporates an injection needle for use with epinephrine.
According to Dr. Joseph Leung's publication entitled “Endoscopic Management of Peptic Ulcer Bleeding”, an “ideal” endoscopic hemostatic device should have the following properties. It should be effective in hemostasis, safe, inexpensive, easy to apply and portable. Thus, cost and non-portability issues associated with laser therapy have generally made it a less favorable treatment for ulcer hemostasis. Consequently, electrocoagulation or thermal coagulation have largely replaced laser therapy as a more routine treatment. Injection therapy generally has an advantage over the above contact thermal devices in that the injection does not need to be very accurate and can be performed through a pool of blood, but the cost of the medication is a disadvantage.
Turning to the argon plasma coagulator, according to in the publication “A Randomized Prospective Study of Endoscopic Hemostasis with Argon Plasma Coagulator (APC) Compared to Gold Probe™ (GP) for Bleeding GI Angiomas”, Jutabha and colleagues compared the efficacy and safety of APC and GP for hemostasis of bleeding GI angiomas and describe the advantages and disadvantages of each type of treatment for angioma patients. Thirty-four patients with angiomas as the cause of acute or chronic GI bleeding, not responsive to iron supplementation alone, were stratified by syndrome (i.e., UGI, LGI angiomas; watermelon stomach; jejunal angiomas; radiation telangiectasia) and randomized to treatment in a prospective study: 16 to APC and 18 to GP.
According to the publication, there were 2 major complications of APC. While there were no significant differences between most clinical outcomes of APC versus GP patients, investigators observed that APC was significantly slower than GP and more difficult to use because of several features of APC: it could not coagulate through blood or water, smoke was common which interfered with visualization and increased gut motility, tamponade of bleeders was not possible, and tangential coagulation was difficult or often blind.
The differences between APC and GP were more marked with multiple angioma syndromes. Although APC is a “no touch technique,” the catheter was difficult to hold 2-3 mm off the mucosa, which affords the best coagulation of a dry field. These features resulted in 6 failures and crossovers with APC and none with GP. There were no major disadvantages of GP except that coagulum needed to be cleaned off the tip after treatment of multiple angiomas. The authors concluded that for hemostasis of bleeding angiomas, both the APC and GP were effective, but there were substantial problems with the newer APC device, and overall the GP performed better.
In light of the above, what is needed is a endoscopic hemostatic device which offers advantages of both the so called non-contact and contact devices and methods without associated disadvantages. Thus, for example, what is needed is an endoscopic hemostatic device which is preferably portable and inexpensive. Furthermore, preferably the device should be capable of tissue contact and tamponage associated with coaptive coagulation to reduce the heat sink effect and facilitate treatment of an eroded artery, but be less likely to induce bleeding when the device is removed from a treated vessel. Furthermore, preferably the device should be capable of coagulation through blood or water (i.e. without contact) as well as tangential coagulation, without generating smoke which raises possible problems of visualization, gut motility or stomach overdistenation. Furthermore, preferably the device should be capable of generating tissue hemostasis at a temperature high enough to result in tissue shrinkage, but at a temperature low enough not to necessarily create char (e.g. dried blood) formation or produce scabs, which maybe subsequently dissolved by digestive juices a result in rebleeding. Furthermore, preferably the device should be capable of use on any surface of the GI tract without regard for orientation. In other words, for example, preferably the device may be used to treat any surface of the stomach, whether above, below or to the side.